1. Field of the Invention
The present invention generally relates to a photolithography process to a glass substrate and a mask thereof, and more particularly to an LCD panel photolithography process and a mask thereof, to prevent the rework and abandonment circumstances of the glass substrate cause of aligning the alignment mark of the wrong mask in the alignment procedure of the lithography system. Accordingly, the manufacture yield rate of LCD panel can be improved.
2. Description of Prior Art
Please refer to FIG. 1. When the LCD panel is manufactured, a lithography system (such as the lithography system of Canon) is used. An issue of a certain shift of the entire patterns occurs in some real manufactures. After the investigation, the reason is that the alignment mark of the wrong mask is aligned in the alignment procedure to result in the abnormal pattern appears. With depth analysis and then the root cause is found, the structure design of the alignment marks inevitably results in such exception. Hereafter, the basic principle of an alignment system of Canon lithography system is introduced below:
Please refer to FIG. 2, which shows a structure diagram of an alignment system. The light generated by the light source passes through the main optical system and reaches the mask and the glass substrate respectively. After reflection, the image of the alignment marks A, C on the mask and the image of the alignment mark B on the glass substrate passes through the objective lens and the alignment scope. Then, these images are fetched by the CCD. Thereafter, the images of the alignment marks A, B, C are transmitted to the image processor and then shown on the monitor. When the center of the alignment mark B coincides with the center of the alignment marks A, C, it means that the alignment procedure succeeds. If the center of the alignment mark B does not coincide with the center of the alignment marks A, C, the load system of the glass substrate is actuated to move the glass substrate till the center of the alignment mark B coincides with the center of the alignment marks A, C. Then the alignment procedure before the photolithography process is completed.
Please refer to FIG. 3 shows a diagram of an arrangement for the alignment marks of different masks according to prior art. In previous masks, the arrangement of alignment marks is linear symmetric designed, even for the arrangement of alignment marks of different masks. Besides, the distances between the alignment marks of different masks are all the same. As shown in the figure, there are alignment marks both at top and bottom of the LCD panels and D2=D3= . . . =Dn (The alphabet n represents the layer of mask). In figure, five masks are illustrated with D2=D3=D4=D5, the design defect in previous masks is when one mask is employed for performing the alignment procedure, but the shapes of the alignment marks of different masks are all the same and the positions are linear symmetric designed. Thereof, the lithography system cannot judge which mask the alignment mark employed in the alignment procedure belongs to. Even the alignment mark of the wrong mask is employed for alignment, the alignment procedure still can succeed and complete. Consequently, the circumstance that the wrong mask is aligned occurs and results in the issue of the certain shift of the entire patterns shown in FIG. 1. In the illustration of five masks with D2=D3=D4=D5, when the second mask is aligned, and the third mask, fourth mask and the fifth mask exist. When the second mask is being aligned, the lithography system misses the alignment mark of the second mask and aligns with the alignment mark of the third mask because the position of the glass substrate is shifted. Because no differences exist between the alignment mark of the second mask and the alignment mark of third mask, the lithography system of the user considers the alignment procedure is completed. Then, the photolithography process is performed and completed. The issue of the certain shift of the entire patterns shown in FIG. 1 occurs due to aligning with the wrong mask. Accordingly, a huge number of the glass substrates have to rework or abandoned and leads to an enormous lost.
Consequently, there is a need to provide an LCD panel photolithography process and a mask thereof.